If the number of items we want is the same as the number of items in the list, then we just return the list. Otherwise we remove a random item from the list and then recurse.

Another Alternative Solution:

Since the above Alternative Solution works by removing things to create the target list, it's most efficient when the target list length is > (orig list / 2). Here's another solution that's efficient in the other way (target < (orig list / 2)) by constructing an accumulator list of selected random elements. (This one also uses removeAt from problem 20)